In recent years, aircraft have been maneuvered in what has become known as a "deep stall" condition which effectively stops the forward velocity of an aircraft while maintaining its attitude in a controlled position. One researcher, Dale Reed of NASA Dryden Flight Research Center, has demonstrated the utilization of "deep stall" by moving horizontal stabilizers (or canards) of an aircraft into a 70.degree. nose down attitude just as the aircraft is flown down to a stall speed. This researcher determined that, if the aircraft is moved rapidly from the 18.degree. angle of attack normal stall to about 28.degree., the aircraft does not have sufficient time to roll off onto one wing. The aircraft subsequently falls downward in a horizontal attitude, under complete control of a downward deflected horizontal stabilizer which is not stalled. The capability of controlling the forward velocity of an aircraft by entering a "deep stall" condition has many uses. One use is the safe landing of long endurance unmanned aircraft (drones). Other uses are relevant to my co-pending patent applications Ser. Nos. 855,285, and 855,303. In these latter-mentioned patent applications, a system for generating an upward air column is disclosed for cooperating with an aircraft that is capable of entering a "deep stall" condition at the top of the air column, thereby becoming captured by the air column. By controlling the pressure of the air column, the aircraft may be gently lowered or raised from a preselected landing area. It would be highly desirable with aircraft to be operated in a "deep stall" condition to have the capability of selectively increasing the surface area of the aircraft wings so that descent of the aircraft can be assisted by the aircraft.